In recent years, a photographic optical device is mounted on a portable device such as a cellular phone. In a case of a portable device, a shake in hand is easily occurred at the time of photographing. Therefore, a photographic optical device which is capable of correcting a shake in hand at the time of photographing has been proposed by the present applicant (see, for example, Patent Literature 1).
The photographic optical device described in Patent Literature 1 includes a movable module on which a lens and an imaging element are mounted, a fixed body which supports the movable module, a shake correction mechanism which is structured to swing the movable module on the fixed body to correct a shake in hand, and a gimbal spring which connects the movable module with the fixed body. Further, the photographic optical device described in Patent Literature 1 includes a photo reflector for detecting a position of the movable module which is capable of swinging. The photo reflector includes, for example, a light emitting diode (LED) structured to emit light toward the movable module and a photo-transistor which receives the light reflected by the movable module and the photo reflector is fixed to the fixed body. In a photo reflector, commonly, a light emitting amount of a light emitting diode varies depending on a supplied electric current and an output current of a photo-transistor varies depending on an amount of the received light.
In order to detect a position of the movable module by a photo reflector, an output current of a photo-transistor (in other words, an output of the photo reflector) is utilized. However, even when a distance between the movable module and the photo reflector is constant, it is difficult to keep an output of the photo reflector substantially constant. The principal reasons are as follows; firstly, the light emitting efficiency of a light emitting diode is provided with an individual difference and, secondly, the sensitivity of a photo-transistor is provided with an individual difference and, thirdly, there are environmental variations such as aged deterioration of the reflection factor of the movable module, change in ambient temperature and the like.
Conventionally, a photo reflector control device has been proposed which is capable of keeping an output of a photo reflector substantially constant (see, for example, Patent Literature 2). In Patent Literature 2, the photo reflector is used for detecting perforations of a photographic film and the photo reflector is disposed so that, when light emitted from a light emitting diode is reflected by a predetermined reflection surface through a perforation, the reflected light is received by the photo-transistor. Further, the photo reflector control device described in Patent Literature 2 controls an electric current supplied to the light emitting diode so that an output of the photo reflector falls within a predetermined range. Therefore, when the photo reflector control device is used, influences of individual differences of a light emitting diode and a photo-transistor (individual difference of an element) and an environmental variation are restrained and an output of the photo reflector is capable of being kept substantially constant.